Method of making magnetic cores



April 19, 1949. G. G. SOMERVILLE METHOD OF MAKING A MAGNETIC CORE Original Filed Jan. '18, 1947 2 Sheets-Sheet 1 M g I I! -Fig.2.

Inventor-z Gareth G. Somer-ville,

His Attorney.

April 19, 1949. G. G. SOMERVILLE METHOD OF MAKING A MAGNETIC CORE 2 Sheets-Sheet 2 Original Filed Jan. 18, 1947 Inventor. Gareth G. Somer-ville,

His Attorney.

Patented Apr. 19, 1949 METHOD or MAKING manna-1c corms Gareth G. Somerville, Pittsileld, Mass assignor to General Electric Company, a corporation of New York Original application January is, 1947, sen-arm.

Divided and this application Novcmber 26, 1947, Serial No. 788,189

This is a division of my application, Serial Number 722,838, filed January 18, 1947, now Patent 2,456,459 issued December 14, 1948, relating to magnetic cores, more particularly to three phase cores for electric induction apparatus, and to a method of making such cores.

An object of the invention is to provide a simple and economical three phase magnetic core having low losses.

Another object of the invention is to provide a three phase magnetic core having improved low loss joints in the yoke.

A further object of the invention is to provide a novel method of making three phase cores which enables the parts to be annealed separately with a good space factor in the annealing oven.

The invention will be better understood from the following description taken in connection with the accompanying drawings and its scope will be pointed out in the appended claims.

In the drawings, Fig. 1 is a side elevation view' make one of the units which are combined to make my core; Fig. 2 is a plan view of the packet shown in Fig. 1; Fig. 3 is a perspective view showing how two of the unitary packets are formed and interfitted for the annealing operation; Fig. 4 shows a detail of the interfitting ends of the units of Fig. 3 after they have been separated and one of them has been reversed preparatory to their recombination for forming a part of the core; Fig. 5 shows how the parts of Fig. 3 are recombined to form a part of the finished core; Fig. 6 is a perspective view of the finished core; Fig. 7 is a detail view of a modification; Fig. 8 is a partial perspective view of the finished modification formed by the parts shown in Fig. '7, and

Fig. 9 illustrates another modification in which the core legs may be provided with joints so that the yokes can be separated from the legs for facilitating the mounting of windings on the legs.

Referring now to the drawings, and more particularly to Fig. 6, the completed core consists of three parallel straight Winding legs I 2 and 3 whose corresponding ends are joined by Y-shaped yokes 4 and 5. The legs are divided or split along their center planes and their extensions which are bent over to form they three radiating legs of the yokes are similarly split. Actually, the core consists of six generally U-shaped bent lamination'type members 6, 'l, 8, 9, l and II. These are arranged in pairs with their ends interfitted so as to form three closed loops whose two halves are in planes making 120 with each other. Thus,

3 Claims. (01. 29-15531) lamination layers to 26, inclusive, are arranged the long parallel sides.

packet of stacked laminations is bent to shape so that when the longest lamination layer is on the outside and the shortest lamination layer is on' the inside, the ends of the laminations will line up with each other. Holes 21 and 28 are punched in the laminations at fixed distances from their ends and the laminations may be aligned and held in proper alignment by means of rods passing throughthese holes. However, the distance between the hole 21 and its end of each lamination layer is diiierent and, as shown, greater than the distance between the hole 28 and its end of the lamination layer. In stacking the lamination layers to form packets, the lamination layers are reversed end for end so that when the hole 21 oi the layer I5 is lined up with hole 28 of the layer I6 and so on throughout the stack, the ends of the lamination layers will be staggered.

In Fig. 3, the parts I0 and I I of Fig. 6 have been formed from two of the packets or stacks shown in Figs. 1 and 2 by simultaneously bending all of the lamination layers in each packet or stack in a suitable press or jig in which suflicient force is applied to cause the bending. The short lamination layers are on the inside and the long lamination layers are on the outside, as indicated. The details of one suitable method of forming the loop shown in Fig. 3 form the subject matter of my application Serial No. 536,748 (D. 71,562) filed May 22, 1944, now Patent 2,456,457 issued December 14, 1948, and assigned to the present assignee. It will be observed that the angles of the abutting ends of the laminations complement each other so that the two U-sh-aped parts Ill and II lie in The loop shown in Fig. 3 is strain relief annealed in an oven and by reason 01' its flat shape, it occupies minimum space in such an oven so that an the parts 6 and! form a loop l2, the parts 8 and 9 form a loop I3 and the parts I0 and II form a loop ll.

The core shown in Fig. 6 may be constructed as follows. Referring to Figs. 1 and 2, a plurality of oven which is loaded with loops of this shape 1 will be operated at good space factor.

together with the member ll reversed, they will fit snugly with the'planes of the parts "I and ii making an angle of 120 with each other so as to form the part I, as shown in Fig. 5.

As has been previously described, the completed core which is shown in Fig. 6 is made by fitting together three of the 120 angle loops shown in Fl 5.

in the modification shown in Fig. 7, the diflerence in length between alternate lamination layers has been increased substantially beyond the width of the lamination layers. Thus, as shown in Fig. '7, the long ends of the lamination layers pass all the way across the interfltting portions of the other core member so as to provide extensions 29. The parts i and H shown in Fig. 7 are otherwise the same as the parts shown in Fig. 5.

In Fig. 8, the parts similar to those in Fig. 6 have been identified by the same reference numerals but these numerals have been provided with primes as theparts are not exactly the same although their relationship is generally the same as in Fig. 6. The extensions 29 interfit with each other as shown in the drawing. This has the advantage over the construction shown in Fig. 6 that there are lapped joints between each half of each leg and at least half of each of the other legs whereas in Fig. 6, there are butt joints between each half of each leg and at least one of the other legs. For example, in Fig. 6, flux in the part 6, which forms one-half of the leg 1, can only get into the leg 2 by way of butt joints as the only connection between three parts l2, l3 and H of the core shown in Fig. 6 is by means of butt joints at the sides of the laminations. Further more, these butt joints being at the sides of the laminations require such flux to move crosswise of the lengthwise lamination of the lamination layers. As the lamination layers are preferably made of grain oriented material having a highly favorable magnetic direction corresponding to the length of the lamination, such crosswise travel of the flux materially increases the losses. An example of suitable material for this purpose is high reduction cold rolled silicon steel. However, it will be observed that in the modification that shorter length lamination members be used and there will be four such members in each lamination layer around the loop shown in Fig. 3.

While there have been shown and described particular embodiments of the invention, it will be obvious to those skilled in the art that changes and modifications can be made without departing from the invention and therefore it is aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. The method of making a three phase mag netic core which comprises, forming at -least three similar cores of flatwise bent laminations, said single phase cores each having two substantially straight leg portions and two substantially straight yoke portions, the yoke portions having parallel 60 deg. bias cut overlapping joints, annealing said single phase cores, opening said single phase cores at their joints, reclosing said single phase cores with one-half of each one turned end for end so that the two halves make an angle of 120 deg. with each other, placing said reclosed single phase cores side by side around a circle so that the adjacent legs of each different pair of said single phase cores form a leg of a three phase core and so that the adjacent yokes of each diiferent pair of single phase cores form a Y-shaped yoke for a three phase core.

2. The method of making a three phase magnetic core which comprises, forming at least three similar cores each having two substantially shown in Fig. 8, the member 6 makes butt and lap joints with the members 1' just as the parts 6 and I make lap joints in Fig. 6 while in addition,

due to the interlocking of theends' 29, the part 6' also makes lap joints with the part 9' so that flux over part 6 can readily get into the part 9' which forms one-half of leg 2'.

The U-shaped members which form the core shown in Figs. 6 and 8 may be provided with separate windings by lacing the individual lamination through the window of the windings until 1 all the laminations are in place. This causes some bending of the lamination but the resulting increase in losses is not excessive.

The increased separation between the two halves of core legs in Fig. 8 can be used as a cooling duct and in the case of liquid-cooled apparatus, liquid can circulate in this space so as to render 'more effective the cooling of the apparatus.

,In the modification shown in Fig. 9, an additional butt and lap joint 30 is shown at the end of aleg portion, such as, for example, 6 or 6' and its correspondingyoke portion 5 or 5'. By

' having such joints in all of the legs, star or,

Y-shaped yoke 5 or 5' can be lifted off as a unitstraight leg portions and two substantially straight yoke portions, the yoke portions having parallel 60 deg. bias cut overlapping joints, an-

nealing said single phase cores, opening said single phase cores at their joints, reclosing said single phase cores withone-half of each one turned end for end so that the two halves make an angle of deg. with each other, placing said reclosed single phase cores side by side around a. circle so that the adjacent legs of each different pair of said single phase cores form a leg of a three phase core and so that the adjacent yokes of each different pair of single phase cores form a Y-shaped yoke for a three phase core, the

joints between the two'halves of each reclosed single phase core being overlapping joints and the joints between each pair of adjacent single phase cores being butt joints.

3. The method of making a three phase magnetic core which comprises, forming at least three similar cores of fiatwise bent laminations, said single phase cores each having two substantially straight leg portions and two substantially straight yoke portions, the yoke portions having parallel 60 deg. bias cut overlapping joints, annealing said single phase cores, opening said single phase cores at their joints, reclosing said single phase cores with one-half of each one turned end for end so that the two halves make an angle of 120 deg. with each other, placing said reclosed single phase cores side by side around a circle so that the adjacent legs of each diflerent pair of said single phase cores form a leg of a three phase core and so that the adjacent yokes of each different pair of single phase cores form a Y-shaped yoke for a three phase core, all magnetic joints in said three phase core being overlapping joints. GARETH G. sormavnm.

No references cited. 

